1. Technical Field
The present disclosure relates to a light-emitting device and an illumination apparatus including the light-emitting device.
2. Description of the Related Art
Since semiconductor light-emitting elements such as LEDs (light emitting diodes) are small, efficient, and have a long lifespan, they show promise as light sources for various products for lighting purposes, display purposes, and so on.
LEDs are used, for example, in LED lamps as a light source for lighting purposes. Examples of LED lamps include bulb-shaped LED lamps (LED bulbs) as an alternative for bulb-shaped fluorescent and incandescent lamps, and straight tube LED lamps as an alternative for straight tube fluorescent lamps. Furthermore, LEDs are used, for example, in LED lighting fixtures which are an alternative for highly directional lighting fixtures such as a recessed light or a spotlight used in shops and the like.
In LED lamps and LED lighting fixtures, LEDs are embedded as a unit in the form of an LED module (a light-emitting device) that emits light of a predetermined color, such as white light.
For example, an LED module for use in bulb-shaped LED lamps and straight tube LED lamps is configured to generate white light with the use of a blue LED chip which emits blue light and a yellow phosphor which emits fluorescence by using the blue light emitted by the blue LED chip.
The amount of a red component contained in white light emitted by such an LED module is small, meaning that the LED module has poor color rendering properties. Therefore, a method of supplementing the above-stated LED module with a red component has been proposed in which a red phosphor that emits fluorescence by using blue light is added to the LED module.
However, the light emission efficiency of the LED module is reduced due to low energy conversion efficiency of the red phosphor. In view of this, instead of adding the red phosphor, a technique of adding a red LED chip which emits red light to improve the color rendering properties is being considered.
For example, Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2011-216868) discloses an LED module that includes a blue LED chip, a red LED chip, and a yellow phosphor. According to this disclosure, the LED module emits white light with excellent color rendering properties.